Method and apparatus of mobile-terminated small data transmission (mt-sdt)

Abstract

A method of wireless communication at a network node and the related apparatus are provided. In the method, the network node first sends a paging message including a first indication of a mobile terminated small data transmission (MT-SDT) for a user equipment (UE) in a radio resource control (RRC) inactive state, and sends data for transfer to the UE while the UE remains in the RRC inactive state. By providing data transmission for UEs in Idle or inactive state, power consumption, latency and system overhead may beneficially be reduced.

What is claimed is: 
     
         1 . An apparatus for wireless communication at a network node, comprising:
 a memory; and   at least one processor coupled to the memory and, based at least in part on information stored in the memory, the at least one processor is configured to:
 send a paging message including a first indication of a mobile terminated small data transmission (MT-SDT) for a user equipment (UE) in a radio resource control (RRC) inactive state; and 
 send data for transfer to the UE while the UE remains in the RRC inactive state. 
   
     
     
         2 . The apparatus of  claim 1 , wherein the network node comprises a centralized unit control plane (CU-CP) and the paging message including the first indication of the MT-SDT is comprised in an F1 application protocol (F1AP) message between the CU-CP and a distributed unit (DU). 
     
     
         3 . The apparatus of  claim 1 , wherein the network node comprises a distributed unit (DU) and the paging message including the first indication of the MT-SDT is comprised in a Uu paging message between the DU and the UE. 
     
     
         4 . The apparatus of  claim 1 , wherein the network node comprises an access and mobility management function (AMF) and the paging message including the first indication of the MT-SDT is comprised in an NG application protocol (NGAP) message between the AMF and a centralized unit control plane (CU-CP). 
     
     
         5 . The apparatus of  claim 1 , wherein the at least one processor is further configured to:
 receive a message from the UE including a second indication for the MT-SDT, wherein the data is transmitted to the UE in response to the message including the second indication.   
     
     
         6 . The apparatus of  claim 5 , wherein the second indication includes one or more of:
 an MT-SDT flag,   a resume cause that indicates the MT-SDT, MT-SDT assistance information, or   a logical channel identifier (ID) associated with the MT-SDT.   
     
     
         7 . The apparatus of  claim 5 , wherein the message from the UE comprises an RRC resume request message. 
     
     
         8 . The apparatus of  claim 5 , wherein the message from the UE comprises an uplink medium access control-control element (MAC-CE). 
     
     
         9 . The apparatus of  claim 5 , wherein the message from the UE further comprises a third indication for mobile originated small data transmission (MO-SDT), the at least one processor being further configured to:
 receive uplink data from the UE while the UE remains in the RRC inactive state.   
     
     
         10 . The apparatus of  claim 5 , wherein the message is received in random access resources associated with mobile originated small data transmission (MO-SDT), the at least one processor being further configured to:
 receive uplink data from the UE while the UE remains in the RRC inactive state.   
     
     
         11 . The apparatus of  claim 1 , wherein the network node comprises a centralized unit control plane (CU-CP), the at least one processor being further configured to:
 receive, from a centralized unit user plane (CU-UP), a downlink data notification that indicates a downlink data amount for the UE, wherein the CU-CP sends the paging message including the first indication of the MT-SDT based on the downlink data amount for the UE indicated by the CU-UP being less than an MT-SDT threshold.   
     
     
         12 . The apparatus of  claim 11 , wherein the at least one processor is further configured to:
 receive the MT-SDT threshold from an access and mobility management function (AMF).   
     
     
         13 . The apparatus of  claim 12 , wherein the MT-SDT threshold is for a protocol data unit (PDU) session, a quality of service (QoS) flow, or a data radio bearer. 
     
     
         14 . The apparatus of  claim 1 , wherein the network node comprises a centralized unit user plane (CU-UP), the at least one processor being further configured to:
 send, to a centralized unit control plane (CU-CP), a downlink data notification that indicates a downlink data amount for the UE.   
     
     
         15 . The apparatus of  claim 1 , wherein the network node comprises an access and mobility management function (AMF), the at least one processor being further configured to:
 send an MT-SDT threshold to a centralized unit control plane (CU-CP).   
     
     
         16 . The apparatus of  claim 1 , wherein the network node is a primary node for dual connectivity with the UE, the at least one processor being further configured to:
 receive an activity notification from a secondary node for the UE that indicates an amount of downlink data for the UE on one or more secondary node terminated bearers, wherein the primary node sends the paging message for the UE in response to the activity notification.   
     
     
         17 . The apparatus of  claim 1 , wherein the network node is a secondary node for dual connectivity with the UE, the at least one processor being further configured to:
 send an activity notification to a primary node for the UE that indicates an amount of downlink data for the UE on one or more secondary node terminated bearers, wherein the primary node sends the paging message for the UE in response to the activity notification.   
     
     
         18 . The apparatus of  claim 1 , wherein the network node is a primary node for dual connectivity with the UE, the at least one processor being further configured to:
 send an MT-SDT threshold to a secondary node for the UE; and   receive an MT-SDT indication from the secondary node, wherein the primary node sends the paging message for the UE in response to the MT-SDT indication.   
     
     
         19 . The apparatus of  claim 1 , wherein the network node is a secondary node for dual connectivity with the UE, the at least one processor being further configured to:
 receive an MT-SDT threshold from a primary node for the UE; and   send an MT-SDT indication to the primary node in response to having downlink data for the UE that is less than the MT-SDT threshold.   
     
     
         20 . The apparatus of  claim 1 , wherein the network node comprises an anchor node that sends the paging message to a serving node for the UE, the at least one processor being further configured to:
 receive, from the serving node, a request to retrieve a context for the UE that includes at least one of a second indication for the MT-SDT or MT-SDT assistance information, wherein the anchor node forwards the data for the UE to the serving node in a UE context response in response to receiving the request.   
     
     
         21 . The apparatus of  claim 1 , further comprising:
 at least one transceiver coupled to the at least one processor and configured to send the paging message.   
     
     
         22 . An apparatus for wireless communication at a user equipment (UE), comprising:
 a memory; and   at least one processor coupled to the memory and, based at least in part on information stored in the memory, the at least one processor is configured to:
 receive a paging message from a network node, the paging message including a first indication of a mobile terminated small data transmission (MT-SDT) for the UE while the UE is in a radio resource control (RRC) inactive state; 
 transmit a message to the network node including a second indication for the MT-SDT; and 
 receive downlink data from the network node while the UE remains in the RRC inactive state. 
   
     
     
         23 . The apparatus of  claim 22 , wherein the second indication includes one or more of:
 an MT-SDT flag,   a resume cause that indicates the MT-SDT,   MT-SDT assistance information, or   a logical channel identifier (ID) associated with the MT-SDT.   
     
     
         24 . The apparatus of  claim 22 , wherein the message from the UE comprises an RRC resume request message. 
     
     
         25 . The apparatus of  claim 22 , wherein the message from the UE comprises an uplink medium access control-control element (MAC-CE). 
     
     
         26 . The apparatus of  claim 22 , wherein the message from the UE further comprises a third indication for mobile originated small data transmission (MO-SDT), the at least one processor being further configured to:
 transmit uplink data to the network node while the UE remains in the RRC inactive state.   
     
     
         27 . The apparatus of  claim 22 , wherein the message is received in random access resources associated with mobile originated small data transmission (MO-SDT), the at least one processor being further configured to:
 transmit uplink data to the network node while the UE remains in the RRC inactive state.   
     
     
         28 . The apparatus of  claim 22 , further comprising:
 at least one transceiver coupled to the at least one processor and configured to receive the paging message.   
     
     
         29 . A method of wireless communication at a network node, comprising:
 sending a paging message including a first indication of a mobile terminated small data transfer (MT-SDT) for a user equipment (UE) in a radio resource control (RRC) inactive state; and   sending data for transfer to the UE while the UE remains in the RRC inactive state.   
     
     
         30 . A method of wireless communication at a user equipment (UE), comprising:
 receiving a paging message from a network node, the paging message including a first indication of a mobile terminated small data transfer (MT-SDT) for the UE while the UE is in a radio resource control (RRC) inactive state;   transmitting a message to the network node including a second indication for the MT-SDT; and   receiving downlink data from the network node while the UE remains in the RRC inactive state.